1. Field of the Invention
This invention in general relates to a process for removing photoresist material and particularly, relates to a process for removing photoresist material in the manufacture of a CMOS (Complementary Metal-Oxide Semiconductor) photosensor.
2. Description of the Related Art
A charge-coupled device is conventionally used in a digital sensor. However, due to the cost and the size of the charge-coupled device, the CMOS photosensor has been recently developed.
A CMOS photosensor is electrically connected with other devices or other CMOS photosensors. A cover layer is used to protect and isolate the photosensitivity area in the substrate to prevent the electrical contact from the contact pad thereon. In such a case, the cover layer comprises a color filter layer for filtering a certain wavelength of light and a polyacrylate layer as a planarization layer or a protective layer for the color filter layer. However, since the properties of polyacrylate are similar to those of the photoresist material, it is difficult to remove the photoresist material by plasma without causing damage to the polyacrylate layer after formation of an opening on the metal pad by photolithography. Therefore, it is suggested that the layer of photoresist material be removed by a solvent.
The result of removing the photoresist material by a solvent depends on the etching machine, because the nature of the photoresist material changes after the ion-bombardment of plasma in the etching process so that the photoresist material cannot be sufficiently removed by a solvent. For example, after the etching process in a Tegal etching machine using low energy plasma, most of the photoresist material can be removed by a solvent, but some hairy photoresist residues still remain. In a TEL etching machine to perform the etching process on the wafer, due to the higher energy of the plasma, most of the photoresist material cannot be removed by a solvent after etching. If any photoresist material is left, the cover layer cannot maintain a planar form. In such a case, the light transmitted through the photosensor is interrupted, and the photosensitivity of the photosensor is thus decreased. Therefore, the complete removal of photoresist material on the cover layer in manufacturing a CMOS photosensor is desired, especially in industry-scale production.
It is therefore an object of the present invention to provide a process for removing photoresist material on an in-process substrate.
It is another object of the present invention to provide a process for manufacturing a CMOS photosensor with high photosensitivity.
To achieve the above objects and other advantages of the present invention, a process for removing photoresist material that leaves no residues and does not damage the in-process substrate is described. The present process for removing photoresist on an in-process substrate comprises the steps of providing a cover layer which is to be etched on the in-process substrate and providing a layer of photoresist material thereon. The photoresist layer is patterned, exposed and developed. Then, the developed photoresist layer is further exposed without using a mask. The cover layer is etched with the use of the patterned photoresist layer as a mask. After etching, the photoresist material is removed by a solvent.
In another aspect of the present invention, a process for manufacturing a CMOS photosensor with high photosensitivity is disclosed. The present process for manufacturing a CMOS photosensor with an in-process substrate having a metal pad for a subsequently formed electric connect comprises the steps of providing a cover layer which is to be etched on the in-process substrate and providing a layer of photoresist material thereon. The photoresist layer is patterned, exposed and developed. Then, the developed photoresist layer is further exposed without using a mask. The cover layer is etched with the patterned photoresist layer serving as a mask to form an opening on the metal pad. After etching, the photoresist material is removed by a solvent.